This disclosure relates generally to improvements in lift truck-mounted, rotatable load handling equipment for picking up, transporting and stacking loads. Such rotatable load handling equipment is usually a load clamp, but this disclosure contemplates other types of rotatable load handling equipment as well such as forks, platens, etc. More particularly, the disclosure relates to improvements in rotator friction braking systems for such load handling equipment which enable a rotator to maintain an intended rotational attitude of a load handler when the rotator is not actuated, even though the load is imbalanced or subjected to dynamic influences.
The compactness of a rotator braking system is particularly important in lift truck mounted load handling equipment to prevent the bulk of the rotator braking system from requiring the center of gravity of the load to be positioned excessively forwardly of the lift truck's front axle. Any excessive forward projection of the load, and thus its center of gravity, can excessively limit the load weight which can be handled by a counterbalanced lift truck without adversely affecting its forward tipping stability about its front axle.
In the past, various types of hydraulic rotators have been used, with or without friction brakes, to rotate lift truck load handling equipment. Such a rotator powered by a hydraulic motor but without a friction brake is shown, for example, in U.S. Pat. No. 5,927,932.
Alternatively, for a number of years, Eaton Char-Lynn has offered a rotator hydraulic motor with one end of its drive shaft connected to a rotary friction brake, and the opposite end of its drive shaft adapted to be connected to a worm screw for driving a lift truck mounted rotator for a paper roll clamp. Although the Eaton friction brake assembly prevents unwanted drifting movement of the rotator when the rotator is not actuated, the friction brake assembly is very bulky with respect to its length and width dimensions, thereby limiting the load-carrying capacity of the counterbalanced lift truck upon which it is used as explained above. In addition, the large size of the Eaton brake assembly dictates low brake-actuating spring pressures and correspondingly low brake release hydraulic pressures, requiring a separate hydraulic exhaust conduit to be routed from the brake release assembly to the lift truck's hydraulic reservoir which occupies further space and creates conduit routing difficulties in the extremely confined space of the rotator assembly.